Award-winning sixth grade science projects include "How we perceive our own voices," "Why are coral reefs dying?" and "The effect of airplane shape, wing shape and wing size on its aerodynamics lift using a wind tunnel." Websites such as education.com and projects.juliantrubin.com feature archives of award-winning science projects.
Julian's Science Fair documents winning projects, collects information on their subjects and materials, and sorts the projects based on approximate grade level. Education.com lists many great sixth grade science project ideas, including projects involving growing crystals and performing electrolysis on water. The list on education.com also contains a great project titled "How Stress Affects the Body."